This invention relates to sumps to contain leakages. In particular the invention is directed to containing leakages of toxic liquids, such as petroleum or other oil based products. A particular application of the technology of the invention relates to protecting the environment from gasoline spills at locations where consumers obtain gasoline at dispensers, pumps and the like.
Current requirements are for periodic testing of leakage around gasoline dispensers at consumer gasoline stations. This means that leakage could occur in between the periods of testing thereby increasing the oil company""s potential liabilities. A reason why current dispenser containment designs can not be tested continuously is because the inside of a dispenser containment box or sump can not be filled with liquid. The liquid would most likely rust the many components inside the box, and the regulatory agencies do not allow standing fluid and the manufacturers do not allow for the kind of weight that would expose the dispenser sump.
Visual inspections to see whether the dispenser sump is leaking is impossible. Also it is desirable to change to requiring a higher form of secondary containment and/or monitoring of liquid. A pipe containing the liquid is termed the first form of containment and the wall of the sump is called the second form of containment.
Presently there are no regulations that require a tertiary form of containment or a monitoring of the integrity of the secondary or tertiary form of containment. This may change if a product, method or system is introduced in the industry with a higher degrees of integrity and protection against leakage than the presently known and used systems, methods and products. The present invention is directed to providing that higher degree or level of containment.
Testing in California for gasoline station secondary systems is to be at initial installation, six months later and every 3 years thereafter. The problem that everyone in the industry faces is how to verify that the system is not leaking. If there is leakage, there is a need to easily trouble shoot to identify where the leakage problem is located. At initial installation of a sump with dispenser, testing is easily accomplished by visually inspecting the box from the outside prior to cementing over the entire job-site. The problem now faced by the industry, as a whole is how do you test secondary containment as simply, reliably without major cost to the end user.
The most commonly used method in the industry is to test the dispenser containment with water filling the containment sump up and utilizing very sensitive float sensors to speed up the test. This involves filling a dispenser sump up with as much as 50 to 60 gallons of water. Should a leak be found the most time consuming issue is then locating the leak that can not be viewed from the outside of the sump since the containment unit is buried in under concrete. Finding and repairing a leak is the most time consuming and costly part of the tests. In addition, the water used must then be removed and treated as a hazardous material adding to the cost and complicates the process of testing.
Other methods of testing that have been considered were vacuum and pressure testing of dispenser containment which are not practical in dispenser containment because of the pipe extending upwards through the opening within the dispenser. The only way to pressurize a conventional dispenser sump is to remove the dispenser which costs over $1,000 per dispenser and the shutdown of the station.
Unlike dispenser sumps, tank sumps can be tested under vacuum and pressure because every part contained within a tank sump can be covered without cost. The test is subject to a much more stringent requirement since air can find much smaller leaks involving electrical wiring leaks and smaller cracks in the sump or its accessories. Air testing usually results in finding leaks in areas that are typically not required to tested by regulators.
The present invention is directed to providing a tertiary form of containment and/or providing a simplified means of monitoring substantially easily and/or relatively continuously the second form of containment.
Another issue relating to sumps, revolves around the need for the piping containing electrical lines into a hazardous material area to be buried 24xe2x80x3 below a concrete surface and the pipe must be made of a continuous run or rigid steel conduit. As a result, the electrical fittings are the most commonly damaged fitting. Even flexible fittings are often bent beyond the recommended entry angle 15 degrees maximum.
Typically, the worst situation is when an electrician needs to run conduit to the side closest to inside of a dispenser containment wall. In addition, a typical 90 degrees minimum bend radius may only be 8 inches. To compensate for inability to bring an electrical conduit close to the wall the electrical contractor often over-loops the conduit by 110 degrees and return it back by 20 degrees to align the conduit with the dispenser above the sump. This typically is a very inaccurate method, which then leads the electrical contractor to abuse the penetration fitting to compensate. This leads to failure of a fitting. An easier method would be to bring the conduit through the bottom of the sump as in shallow pans, which alleviate stress to the fittings. However, this also leaves the fitting on a bottom of a sump exposed to fuels that may breakdown the seals leading to an earlier failure.
The invention is also directed to having an improved technique for passing piping and conduits into and through a sump wall and to retain integrity and alignment with a dispenser above the sump.
These objects and other objects of the invention are achieved by the invention in the manner set out below.
According to the invention, there is provided a sump for inhibiting leakage of liquid contained therein. There is a double wall for at least part of the sump. The sump defines a cavity for containing liquid. There is an interstitial space between the double wall. An indicator liquid is located in the space.
A sensor is in fluid communication with the interstitial space such that a change in the pressure or liquid level in the interstitial space causes the sensor to indicate leakage into or from the interstitial space.
Also according to the invention the sump includes a base, and a wall directed upwardly from the base of the sump towards the top, thereby forming a cavity for liquid.
An angular portion of the upwardly directed wall is directed at an angle from the base greater than 90 degrees and a remote location of that angular portion is connected with an upright wall to the sump.
According to the invention there is provided a system of dispenser containment utilizing a primary, namely an inner, and a secondary, namely an outer, wall. An interstitial space between the two walls traps an interstitial fluid to test the integrity of the dispenser containment and the fittings that pass through the walls.
Preferably a minimized quantity of fluid is located in the interstitial space. This is achieved by retaining the interstitial space as relatively small as possible. This makes the change in the liquid level in the space enhance changes in the level to find small leaks quickly.
In large dispenser sumps {fraction (1/10)} of a gallon change allows one to visually see a change of 1xe2x80x3 in the level of a manometer or electronic sensor associated in fluid connection with liquid in the interstitial space. The interstitial test fluid is permanently left inside the interstitial space thereby eliminating the need and cost to treat hazardous material cost and virtually eliminating the dispenser containment tests.
Preferably, a manometer is employed. The manometer can be used to identify the height at which a leak can occur. This reduces the time to trouble shoot. The manometer can be used to measure small volume changes either visually or through electronic float sensors. The visual inspections are performed without the introduction of any water inside of the dispenser sump. The manometer can permit for visual or electronic monitoring on an intermittent basis or on a continuously basis. Manometers are also preferred because the amount hydraulic pressure is relatively limited by the height over the lowest point.
The manometer is removable because the manometer may be damaged and require to be replaced. Plastic is a preferred material because if during the installation a pipe wrench hit the tubing, the manometer may break before causing damage to the more expensive containment sump.
The manometer placement at the lower part of the sump is preferred. Testing of the sump with air pressure or vacuum or even helium requires the interstitial fluid must be removed first from the lowest point in the dispenser containment interstitial. Once removed, the alternative tests are helpful in pinpointing leaks within the sump.
The secondary wall, namely the outer wall, also allows relatively easier trouble shooting using a variety of methods such as manometer measurement, or pressure/vacuum or helium measurement.
Should a sump box leak somewhere on the outside it is likely there was no release of gasoline to the ground because of the redundant seals in a double wall dispenser containment. Repair to dispenser sump""s fittings is a common problem and is easily repaired inside dispenser containment with the present invention.
Brine or Propylene Glycol solution is the preferred interstitial fluid because of the reduced likelihood of damaging effects of liquid freezing, namely expanding, within the interstitial of double wall dispenser containment and it is non-toxic. When filling the dispenser containment with brine solution as purging air from the upper extremity is effected. A breathing hole allows air to escape and allows the brine to completely fill the interstitial space. The purging of air prevents volume fluctuations due to air temperature fluctuations. This helps minimize false alarms especially on double wall dispenser containment with electronic level detectors.
A breather hole may need to be open because it will show leakage better. In other cases, the hole is closed to ensure a more redundantly sealed system.
The configuration of container on the sump box with an angular portion has an internal angular relationship with adjacent walls on either side of about 135 degrees and has advantages. This degrees relationship is akin to an outside angular relationship of 45 degrees angle at the bottom of the sump box and the upright of the sump box. This relationship has valuable beneficial advantages to an electrical contractor fitting electrical conductors and pipes in and through the sump box.
The foregoing and other objects, features, and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments which makes reference to several drawing figures.